Thermoset vs thermoplastic
End-users and dealers often confuse thermoset vs. thermoplastic materials. Despite appearing similar, these plastics behave differently. The initial forming of a thermoset cannot be redone, but it is possible with a thermoplastic. This is a critical consideration in CNC machining of thermoplastics and thermosets.
This property is evident from the higher heat deflection temperature (HDT) and melting temperature for thermosets. It also extends to the types of applications for the two. Thermosetting plastics are well-suited for high-performance applications, such as aerospace and automotive parts. Thermoplastics are broader in their application range; they are used in cookware, medical devices, packaging, and other areas.
More about these and other differences is covered next, but let’s first learn about each of these materials.
What is Thermosetting Plastic?
A thermosetting plastic, thermosetting polymer, or simply a thermoset, is a type of plastic that undergoes an irreversible curing process. Cross-linking creates a strong 3D network comprising powerful bonds.
Thermoset cross-linking structure
These powerful bonds make thermosetting plastics incapable of being remolded after the curing stage. Also, the plastics have incredible resistance to chemical attacks and heat. The superior structural integrity of this type of plastic, even in harsh environments, is the biggest reason manufacturers use it for demanding applications.
The main properties of thermosetting polymers are;
- High hardness and rigidity
- High thermal resistance
- Excellent electrical insulation
- Superior rigidity
- Chemical stability
Thermosets are available in various categories, including melamine, silicone, epoxy resins, and polyurethane. More on the types of thermosetting polymers is covered below.
The Types of Thermosetting Polymers
The main categories of thermosetting polymers are polyurethanes, silicone resins, amino resins, polyester resins, phenolic resins, and epoxy resins.
Polyurethanes
These thermosetting polymers are versatile. They can be malleable or soft based on the formulation process. For this reason, polyurethanes are ideal for custom manufacturing.
Polyurethane parts
Key properties of this polymer category are abrasion resistance, impact resistance, water stability, and flexibility at low temperatures.
Silicone Resins
Silicone resins have a cross-linked structure. Their main characteristics include dielectric properties, low surface tension, and outstanding weather resistance. These thermosetting plastics are used to manufacture quality weather-resistant sealants and electrical insulation parts.
Amino Resins
The most notable properties of amino resins are scratch resistance, insulation, and rigidity. You can order parts made of ARs for toilet seats, sockets, bowls, and kitchen worktops.
Kitchen worktop
Polyester Resins
PRs are renowned for their good insulation, stiffness, and hardness. They are primarily in the manufacture of glass-reinforced plastics. Kayaks are made from this reliable thermosetting plastic.
Phenolic Resins
These plastics are hard but easy to shape into complex shapes. They are also heat-resistant. Manufacturers use them for snooker balls, gears, and bottle lids, among other parts.
Phenolic resin gear
Epoxy Resins
Epoxy resins (ERs) are heat-resistant, chemical-resistant, and good electrical/thermal insulators. However, these plastics are prone to breakage on impact due to their brittleness. Contact us for more information about these thermosetting polymer plastics and their potential applications in your projects.
Benefits of Thermoset Plastic
Consider the following advantages of thermoset plastic.
- Chemical resistance
- Electrical insulation
- Heat resistance
- Structural integrity
Limitations of Thermoset Plastic
These plastics have the following limitations.
- The curing process is irreversible.
- Brittleness
- Processing complexity
Applications of Thermoset Plastics
Thermosetting materials have significant applications in numerous industries. Thermoset plastic examples are found in electrical/electronics, construction, wind energy, industrial sector, household equipment, automotive, and aeronautical sectors.
Electrical/Electronics: For their heat resistance and electrical insulation, thermosetting plastics are used to make switches, sockets, enclosures, connectors, terminals, and printed circuit boards (PCBs).
Electrical wire insulation
Construction: This industry relies on the chemical and moisture resistance of thermosets in pipes, high-pressure laminates (HPL), and polyurethane foams, among other applications.
Wind Energy: Polyester resin or epoxy wind turbine blades are resistant to corrosion, chemical degradation, and fatigue. They also have a high strength-to-weight ratio.
Industrial Sector: In high-temperature environments with various chemicals, thermosets are instrumental. These materials are used for components such as gears, rollers, and molds.
Household Equipment: Thermosets are used in household equipment for various applications, including handles, electrical components, oven internal coatings, countertop surfaces, and buttons.
Automotive: Thermoset plastics are found in many automotive parts, including structural reinforcements, battery casings, engine covers, and brake pads.
Aeronautical: For this demanding industry, you can use thermosets in wing structures and airframes. These are some of the areas where low weight and optimal safety are critical considerations.
What is a Thermoplastic?
Thermoplastics are another category of polymers, which are renowned for their capability to be reheated, remelted, and reshaped, and still retain their chemical structure. They have a unique molecular structure defined by weak forces between monomers, as illustrated in the image below.
Thermoplastic molecular structure
Read more about more categories of polymers from this comparison:
Different Types of Thermoplastic Polymers
The market offers several types of thermoplastics, including ABS (acrylonitrile butadiene styrene), polycarbonate, acrylic, polyvinyl chloride, polystyrene, and polyethylene. Each of these thermoplastic examples has unique properties, which suit specific applications.
Here’s a table highlighting these types of thermoplastics.
| Thermoplastic | Properties and Typical Applications |
| ABS |
|
| Polycarbonate |
|
| Acrylic |
|
| Polyvinyl Chloride |
|
| Polystyrene |
|
| Is polyethylene a thermoplastic? Yes, it is. |
|
Is PVC a Thermoplastic or a Thermoset?
PVC is a thermoplastic, a fact evidenced by its ease of softening when heated and turning into a fluid with additional heat. It is an amorphous polymer alongside options such as acrylic, polycarbonate (PC), and polymethyl methacrylate (PMMA).
Benefits of Thermoplastic Polymers
These polymer plastics offer the following benefits;
- Easy to process
- Lightweight
- Great design and manufacturing flexibility
- Easy to recycle and reuse
- Impact resistant
Limitations of Thermoplastic Polymers
These are the common drawbacks of thermoplastics;
- They tend to melt or soften at high temperatures
- Typically more expensive than thermosets
Applications of Thermoplastics
Here are the most common applications of thermoplastics, which include the automotive industry, the construction industry, the packaging industry, and the consumer goods industry.
Automotive Industry: Thermoplastic materials are used to manufacture lightweight parts such as piping systems and fuel tanks. They help enhance the fuel efficiency of cars.
Construction Industry: Thermoplastics are extensively used for insulation and pipes. The industry values the materials for their ease of installation and corrosion resistance.
Packaging Industry: The food and beverage packaging spaces require flexible and easy-to-shape materials, which are available in the form of thermoplastics.
Thermoplastic food packaging containers
Consumer Goods Industry: When it comes to consumer goods, the smooth surface, clean appearance, and shaping capability of thermoplastics are valuable. Examples of items are toys, office components, and lighting fixtures.
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Thermoset vs. Thermoplastic: Which Type of Plastic Should I Use?
To get optimal performance, longevity, and cost-effectiveness from the two plastics, the main considerations are chemical composition, structure, melting point, processing/manufacturing, reusability, and applications.
Thermoset vs. Thermoplastic: Chemical Composition and Structure
The first point to remember is that thermosets and thermoplastics have different chemical compositions and structures. These core differences determine how the plastics behave when cured. For thermosets, the structure is defined by permanently cross-linked 3D polymer chains. The chemical bonds cannot be reversed once they are formed during curing. This irreversibility is what differentiates thermosets from thermoplastics.
Thermoplastics feature linear polymer chains. These chains are relatively weaker compared to the 3D polymer chains of thermosets. They can effortlessly slide across each other when heated. Since the bonds between the linear polymer chains are temporary, thermoplastics can be easily remelted and reshaped.
Thermoset vs. Thermoplastic: Melting Point
The degradation temperature for thermoplastics is higher than the melting temperature. Therefore, these materials soften when heated, say with hot water. They also solidify when the heat is removed.
The boiling water effect on a PVC pipe
In contrast, thermosets do not melt again after curing. Unlike thermoplastics that have a low melting point, thermosetting plastics cannot be reformed.
Thermosetting vs Thermoplastic Polymers: Processing and Manufacturing
Processing and manufacturing thermosets and thermoplastics is a matter of temporary vs permanent and cost-effective vs. expensive. Curing thermosets is a demanding process that requires a means to permanently set the plastic. Manufacturers use techniques or solutions such as heat or radiation.
Given that thermoplastics can be reheated and reshaped, they have several processing methods. Injection molding, 3D printing, and extrusion are popular processing technologies for thermoplastics. You can get quality plastic CNC machining services for the two plastics.
Thermoset vs. Thermoplastic: Reusability
There is an intensified focus on sustainability and reusability of parts, so there is a related debate for thermosets and thermoplastics. The higher reusability and recyclability of thermoplastics are non-contestable.
A plastic recycling plant
While thermoplastics can be repeatedly and easily reused, the process is more complicated for thermosetting plastics. That said, it is important to highlight that concerted efforts are being made on all plastics to reduce the environmental impact. Lifecycle management strategies are being applied across the industries for more efficient and responsible use of thermoplastics and thermosets.
Thermoset vs. Thermoplastic: Ideal Applications
Thermosets are ideal for high-performance applications. Such applications require parts with high structural reliability, heat resistance, and chemical stability. That explains why thermosetting materials are common in electrical insulation and aerospace parts.
But for versatile and easy-to-manufacture parts, thermoplastics are generally recommended. The plastic type is preferable for complex parts. Recycling the material is also relatively straightforward. Typical thermoplastic parts are screws, medical devices, and electronic parts.
Are Thermoplastics Stronger Than Thermosets?
No, thermosets generally have a higher mechanical strength than thermoplastics. They also have higher dimensional stability. Thermosets maintain these properties better than thermoplastics do after curing.
Strong thermoset composite
Which is Cheaper, Thermoplastic or Thermoset?
Considering the manufacturing costs, thermoplastics are often more affordable than thermosetting plastics. This is true and relevant only to a certain degree. However, part performance, strength, and durability are other factors to consider before choosing between the two.
When it comes to material costs, again, thermoplastics have an advantage. Thermoset plastic raw materials are more expensive. The manufacturing process for thermosets is also more time-consuming. Thermoplastics allow rapid prototyping and high-volume manufacturing.
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Summarized Table of Thermosetting vs Thermoplastic Polymers Differences
As the table below summarizes, thermoplastics and thermosets differ in their processing methods, melting points, head deflection temperatures, reformability, and material costs. Other comparison areas are recycling and common applications.
| Property | Thermoplastic | Thermoset |
| Heat Deflection Temperature (HDT) | Lower compared to thermosets | Superior HDT |
| Melting | Softens and hardens when heated and cooled, respectively | Does not melt; degrades at high temperatures |
| Reformability | Can be remelted and reshaped several times | The curing process is irreversible |
| Processing Methods | Extrusion, injection molding, 3D printing | Heat or radiation curing |
| Manufacturing speed | High-volume production and rapid prototyping | Slower manufacturing process |
| Material cost | Generally more cost-effective | More expensive |
| Reusability & Recycling | Easy to recycle repeatedly | More complicated to recycle |
| Best for | ease of machining complex, versatile parts | Chemical stability, heat resistance, structural stability |
| Common applications | Cookware, packaging, medical parts, electronic parts, and screws | High-performance applications – automotive parts, aerospace parts, |
In Conclusion
This guide has highlighted the differences between thermosets and thermoplastics. The capability of thermoplastics to be repeatedly melted and shaped sets these types of plastics apart. Furthermore, thermoplastics are cost-effective, easy to process, impact-resistant, and ideal for recycling.
Curing thermosets is a once-for-all process; it cannot be reversed. If reheated, the material simply degrades. But the plastic type has many positives, including dimensional stability, heat resistance, and chemical resistance.
ProleanTech prides itself on offering world-class CNC machining services for plastics. Yes, cost is a driving factor, but we also help customers look at the plastic’s physical properties, chemical properties, and mechanical properties.
For more on these services, get in touch with our experts today.
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